This disclosure relates to a turbine engine speed sensing system.
Speed sensing systems are used in a multitude of machines to measure a rotational speed of a component, for example. In aerospace applications, such as auxiliary power units or turbo machines, a speed sensing system is typically used to measure the rotational speed of a turbine and/or compressor.
In one example auxiliary power unit, a speed probe is arranged in proximity to a shaft to sense the rotational speed of the turbine. An analog speed signal from the speed probe is provided to a speed circuit, which converts the analog speed signal to a digital speed signal. The digital speed signal is provided to a microprocessor and/or firmware, which controls operation of the auxiliary power unit based upon the speed signal.
The speed probe output voltage can vary outside of acceptable margins due to a component failure, which can result in the speed circuit producing a digital signal that does not represent an accurate detection of speed. For example, it is possible for an analog output voltage from the speed probe, which provides the speed signal, to become too low, which can result in an over-speed condition.
Complex sensor error detection systems have been developed to identify faulty sensors. For example, a neural network can be used to learn the sensing system norms, which can then be used to determine error and provide compensation for the error. Such systems are very complex and rely upon information from numerous sensors and systems.
What is needed is a speed sensing system that is less susceptible to certain failure modes, but is not unduly complex.